The official line from DVSA is this: 'You can only drive a vehicle with a SORN on a public road to go to or from a pre-booked MOT or other testing appointment. You face court prosecution and a fine of up to £2500 if you use it on the road for any other reason.' You say that you haven't evaded any tax, but technically you have. You didn't apply to DVSA for a change of taxation class (to 'Historic'), which means you weren't eligible for free VED at the time. You have therefore failed to pay for the VED that was due. Anybody whose car is old enough to be classed as 'Historic' needs to ensure that the taxation class is changed. Until this is done, your car isn't 'tax-free'. In an ideal world this would happen automatically - but nothing is ideal when it comes to the DVSA. The onus is on the registered keeper of the vehicle to apply for 'Historic' taxation. It's also worth remembering that SORN no longer needs to be renewed annually, and now remains in place until you next tax your car.